A method, a computer program, a memory medium, and a controlling and/or regulating system are described in German Patent Application No. DE 44 26 020.
During operation of internal combustion engines, monitoring of all exhaust gas treatment components for OBD limiting values, which are mostly specified as a multiple of an emission limiting value, is required by law within the scope of an on board diagnosis (OBD). Coated catalytic exhaust gas treatment components such as oxidation catalytic converters, NOx accumulator-type catalytic converters, or coated particulate filters must be checked for their operability. Most of the known approaches use temperatures, which are determined for points upstream and downstream from a catalytic converter, in order to evaluate a measure for the completeness of an exothermal reaction in the catalytic converter. This measure is used as the measure for the operability of the catalytic coating or the catalytic converter.
In order to achieve reliable diagnostic results, German Patent Application No. DE 44 26 020 provides a diagnosis in a predetermined operating state of the internal combustion engine, in particular an operating state having a low exhaust gas mass flow rate. The model temperature, used in addition to the measured temperature, may be formed either on the basis of a fully non-operational catalytic converter, a fully operational catalytic converter, or what is known as a borderline catalytic converter, the borderline catalytic converter having an operability which is between these extremes (fully non-operational, fully operational). By definition, the borderline catalytic converter has an operability which just about meets or just about no longer meets the statutory requirements for its conversion capability. In any event, German Patent Application No. DE 44 26 020 provides only one single difference of values of one measured temperature and values of one single model temperature.